TOPIC FOURTOPIC FOUR

Reproduction and Reproduction and DevelopmentDevelopment

A. Asexual A. Asexual reproduction: reproduction: a a method of method of reproduction in which reproduction in which all the genes passed all the genes passed on to the offspring on to the offspring come from a single come from a single individual or parent individual or parent

1. Advantages: faster, 1. Advantages: faster, easiereasier

2. Disadvantage: no 2. Disadvantage: no variety. Offspring are variety. Offspring are the same as parent.the same as parent.

Hydra budding

B. Sexual reproduction: B. Sexual reproduction: a method of a method of reproduction that involves two parents to reproduction that involves two parents to produce offspring that are genetically produce offspring that are genetically different from either parent different from either parent

1. Advantage: variety1. Advantage: variety 2. Disadvantage: more time, effort and 2. Disadvantage: more time, effort and

risk.risk.

C. Mitosis: C. Mitosis: the process that divides the the process that divides the cell's nucleus into two, each with a cell's nucleus into two, each with a

complete set of genetic material from complete set of genetic material from the parent cellthe parent cell

1. Asexual1. Asexual 2. One division produces two identical, 2. One division produces two identical,

diploid (2n) cells.diploid (2n) cells. 3. Chromosome number in the daughter 3. Chromosome number in the daughter

cells is cells is the same the same as in the parent cell.as in the parent cell. 4. Large organisms use mitosis for 4. Large organisms use mitosis for

growth and healing. Simple organisms growth and healing. Simple organisms use it touse it to

reproduce.reproduce.

D. Meiosis: D. Meiosis: the process that results in the process that results in the production of sex cells (sperm and the production of sex cells (sperm and

egg) egg) 1. Sexual reproduction1. Sexual reproduction 2. One cell divides 2. One cell divides twice twice to make four to make four

DIFFERENT cells.DIFFERENT cells. 3. All 4 cells have half the number of 3. All 4 cells have half the number of

chromosomes found in the parent cell.chromosomes found in the parent cell. 4. Makes 4. Makes gametes gametes (sex cells). In humans 4 (sex cells). In humans 4

sperm cells or 1 egg and three non functioning sperm cells or 1 egg and three non functioning cells are produced each time meiosis occurs.cells are produced each time meiosis occurs.

5. Separates pairs of 5. Separates pairs of homologous homologous chromosomes chromosomes so that offspring get oneso that offspring get one

chromosome of each pair from a different chromosome of each pair from a different parent.parent.

E. Fertilization E. Fertilization occurs in the occurs in the oviductoviduct. A fertilized egg is called a . A fertilized egg is called a zygote zygote and has aand has a

normal number of chromosomes.normal number of chromosomes.Click on

diagram to view

animation

Click on the images below to compare Mitosis with Meiosis

F. F. The fetus develops in the The fetus develops in the uterusuterus. . Cells divide without becoming larger Cells divide without becoming larger (cleavage). After a few days, cells begin (cleavage). After a few days, cells begin to to differentiate differentiate – that is they start to – that is they start to form different types of cells (nerve, skin, form different types of cells (nerve, skin, bone, etc). At this stage the embryo is bone, etc). At this stage the embryo is very vulnerable to alcohol, drugs, etc very vulnerable to alcohol, drugs, etc because the important organs and because the important organs and systems are just starting to develop systems are just starting to develop